First I would double check that someone hasn't been editing the
AllItems.aspx page  in the library  with SharePoint Designer. That would
explain both why there are no items listed  and no menus.

Second, I would go into the library settings  and check to make sure that all
the files  aren't CheckedOut with no checked  in version using the CheckedOut
files link in the library settings. If someone added a required meta data
field or replaced the content  type in the library the files could all be
checked out with no checked in version. Such files are only visible to the
original author and on a custom listing in library settings. If that is the
case then the files need to be checked in manually and any additional
metadata added or a content type chosen.

Those are the first two issues that come to mind.

I would even go so far as to check whether someone "closed" the list web part
and then freaked out and added the web part back. If the view they used was one
that doesn't show anything then maybe that's your issue.

Site Settings-->Edit this page...-->Add a web part-->At the bottom of the dialog
box is a link to the Advanced Web Parts Gallery. In there you might find  the
Closed Web Parts link. If it contains a web part with the lists name then you
found your culprit.

I would even go so far as to check whether someone "closed" the list web part
and then freaked out and added the web part back. If the view they used was one
that doesn't show anything then maybe that's your issue.

Site Settings-->Edit this page...-->Add a web part-->At the bottom of the dialog
box is a link to the Advanced Web Parts Gallery. In there you might find  the
Closed Web Parts link. If it contains a web part with the lists name then you
found your culprit.

Almost everything in SharePoint 2007 is done with Web parts.